Many methods are implemented in industry for controlling production/distribution lines, not only for detecting problems arising on transport paths but also reliably determining a quantity of items produced or distributed on said lines. Particularly, some of these methods are used for ensuring proper dispatching or packaging of said items, or even further allowing accurate billing or tax accounting of the items so produced or distributed.
Imaging devices are of common use for controlling production of items on automated production lines. For example, on bottling lines, strobe light (using a LED lighting unit controlled by a laser trigger device which detects presence of an item, for example) illuminates bottles transported on a conveyor and marked with a barcode (1D or 2D barcode, like SKU code or data matrix, for example), and digital cameras take digital images of the so illuminated bottles. A strobe light source typically uses a LED lighting unit controlled by a laser trigger device, which detects the presence of an item. Conventional image processing means then automatically detect on a digital image of an item a region of interest containing a barcode pattern and then identify the item by decoding the detected barcode. Such identification may be used, for example, for correctly labeling the above bottles according to their type (or content, etc.). There are many known techniques relating to image processing which can be used for identifying an item marked with an identifier (including item identification data) from a digital image of said identifier.
The above imaging devices, or readers, may be adapted to read identifiers from light reflected or emitted by said identifier within any optical wavelength range between the UV (ultraviolet) and the IR (infrared).
There are also many other well known techniques adapted to different types of identifiers. For example, a RFID reader is adapted for reading identifiers like RFID tags disposed on items, these RFID tags including item identification data (possibly encrypted). As another non-limiting example, the identifier may be a magnetic marking, and the corresponding adapted reader is then of magnetic sensor type.
Thus, whatever specific type of identifier including identification data is used for marking items transported on a production/distribution line, an adapted type of reader is used for reading said identifier and sending a corresponding reader signal to a controller having processing means capable of extracting identification data from said reader signal.
Most often, items on a production distribution line are transported (for example, on a conveyor) arranged according to a given disposition all along a transport path. This given disposition may correspond to items in single file, or may be different, like for items grouped in columns or any other geometrical disposition. The items may as well be transported by batch, the items having said given disposition within the batch. As a non-limiting example, the items may be transported already packed by batch within a packaging adapted for allowing a reader to read identifiers on the items. As an illustration, for example in case the items are cigarette packs, and the identifier is a barcode printed on the pack (or on a label stuck on the pack), said adapted packaging may then be a transparent film wrapped around a batch of cigarette packs so that an optical reader can read the barcodes through the film.
Generally, in case a distribution of items, or a packaging of items, possibly by batch of a given number N (N≧1) of items, is carried out on a production/distribution line, the items are transported arranged according a given disposition along a transport path from a first zone toward a second zone on the line, each transported item being marked with a unique item identifier including unique item identification data of the item, the items transported from the second zone are then collected by a collector device (like a pusher, for example) to form a batch of a given number N of said items. The collector device generally includes a sensor operable to detect that a batch of N items has been formed (for example, a mechanical counter, or an electronic counter in which a light beam between diodes is interrupted by a transported item). This sensor is operable to deliver a batch signal each time a batch of N items has been counted. Operations on the line are generally controlled by a controller. Also, mounted on the line, at the level of the first zone, a reader connected to the controller typically reads the unique identifier on each one of the items within said first zone, and sends corresponding reader signal to the controller. The controller has processing means capable to extract each unique item identification data from the received reader signal in accordance with an ordering corresponding to said given disposition of the items. These processing means may in fact be split, for example, between the controller itself and the reader (i.e. some processing steps of the reader signal being then executed at the reader), or may even involve a remote connected processing unit.
As an example, in case the items are transported in single file and the identifier is a barcode, the reader classically comprises a camera (or a plurality of cameras around the first zone, and possibly including illumination source for illuminating the items to be imaged) set for reading a barcode on one item at the time crossing the first zone, by taking a digital image of a region of interest containing the barcode on the (illuminated) item. Many known methods are available to be used by the processing means for detecting and decoding the digital image of the barcode sent by the reader. As another non-limiting example, in case the items are transported grouped according to a given disposition, the first zone has an extension covering a group of items, and the reader may be a camera capable to take a digital image of a group of items in the first zone, as known in the art. Then the processing means are capable to detect each barcode within the digital image, and extract the corresponding identification data for each item according to an ordering which corresponds (by a one-to-one mapping) to the respective positions of the items within the group.
In the above conventional production/distribution line, due to physical constraints it may be not possible to bring the first and second zones closer together with each corresponding reading equipment, particularly to allow maintenance by technicians of said reading equipment and also of the sensor and collector device near the second zone, without excessive perturbation of the line. Indeed, for reading each item crossing the first zone, generally at high speed on modern production/distribution lines, the real-time reader equipment is quite sizable.
However, due to quite frequent jams on the line causing loss or deterioration of items, or even due to fraudulent interception of items between the two zones, it is not sure that all the items identified by the reader in fact correspond to the items counted at the sensor level, i.e. after the second zone. Thus, problems are generated in case items having being identified on the line (and thus, possibly accounted for taxation, or billed as being delivered) are lost before being collected by the collector device, or in case the collected batches of items in fact contain unidentified items and are nevertheless distributed, or packaged.
Consequently, the above conventional controlling of operations is not well adapted to real-time item identification, particularly on high speed production or distribution lines, and especially if every single item passing on the line needs to be identified.